Machines for the aforedescribed purpose, i.e. for metering and filling viscous or pasty products and especially for the filling of product assortments like fruit yogurt containers for various fruits or fruit combinations, and preferably in multirow aseptic machines, generally have for each row of containers advanced past a filling station, a respective metering device which is connected to a supply of the product to be packaged and has an outlet for a metered amount of the packaged product. The control of the flow of the product is effected by a product. The control of the flow of the product is effected by a valve slider having a valve stem and a metering piston is provided for displacing a fixed quantity of the product at each stroke through the outlet and into the container, as controlled by a piston rod connected to that piston.
An apparatus of this type is described in German printed application DE-AS 23 21 206.
In the metering device of this apparatus, the metering piston and a the control band are received in respective cylinders which are axially and laterally offset from one another. The metering piston and its piston rod and the control valve and its valve stem are guided in respective caps closing individual cylinders and having different types of seals, for example, the metering piston and a sealing sleeve of a bellows type.
The sealing devices for both piston rod and the valve stem of this earlier arrangement have significant drawbacks, especially when the sealing effect breaks down.
The result is significant inaccuracy in metering of the product into the container. In practice, considerable work and time are required to dismount the seals and replace them when wear necessitates such replacement.
Wear of the seals is especially pronounced when assortment packaging is carried out. In such cases, the individual rows of containers are filled with different products, for example, fruit yogurt containing raspberries, fruit yogurt the yogurt, the high seed content gives rise to more rapid wear of the seal than is the case where products with lesser amounts of seed or seedless products are packaged and hence the seals more prone to wear must be replaced more rapidly.
In practice it is found that certain seals must be replaced to avoid problems in the metering and filling operation while others may not have to be replaced.
In practice, however, all seals at the metering pistons are replaced whenever the machines are brought down for a seal change.
In a filling machine of the multiple-row type, this seal replacement, utilizing the conventional machine construction, can take considerable time and for that period of time the machine must be out of production. Since the disassembly of the upper part of the individual cylinders is complex and time consuming, the time required for seal change is excessive. Furthermore, cleaning of the earlier metering unit by flushing the valve and piston or plunger from all sides cannot readily be carried out.
While in our opinion DE-AS 23 21 206 represents the closest art of which we currently have knowledge, mention may be made of German patent DE 38 17 418 and German open application DE-OS 23 21 205 which respectively show another multirow filling machine and a structure similar to that of DE-AS 23 21 206, as state of the art.